Burner ignition and safety control system



May 9, 1950 J. 5. BAKER BURNER xcnmou AND SAFETY CONTROL SYSTEM Filed June 5, 1946 7" jwaamg Patented May 9, 1950 BURNER IGNITION AND SAFETY CONTROL SYSTEM John S. Baker, Chicago, Ill., asslgnor to Cook Electric Company, Chicago, 111., a corporation of Illinois Application June 5, 1946, Serial No. 674,579

18 Claims. I

The present invention relates to furnaces and has special reference to control apparatus for gas fired furnaces.

More particularly, this invention relates to safety control means for preventing the accumulation of gas in the furnace which, if ignited, might result in an explosion. The control means may comprise ignition apparatus such as a spark plug which is constantly energized at regular short intervals to ignite gas entering the furnace from any cause whatsoever before there is a sumcient accumulation thereof to result in an explosion. In addition, control means are provided which act to close or prevent opening of the main gas supply valve in case of any failure of the ignition means. An accumulation of gas in the furnace is therefore prevented by igniting any gas entering the furnace or, if there is any failure in the ignition means, by completely shutting off the supply of gas by closing the main gas supply valve.

Heretofore gas fired furnaces have been subject to explosions resulting from the ignition of gas which has accumulated therein from causes such as leakage of the main gas control valve, failure of he ignition system or pilot or as the result of the fiames being extinguished while the main gas control valve was open. If the furnace, with an accumulation of gas therein, is ignited by the actuation of the ignition means or by any other means, serious damage may ensue.

The supply of gas to the furnace is controlled by a main gas supply valve, the operation of which is normally controlled by a temperature responsive device such as a room thermostat through the intermediary of a solenoid associated with the valve. When heat is called for, the thermostat effects energization of the solenoid to open the valve and when no heat is called for, the solenoid is deenergized and the valve is closed.

The gas supplied to the furnace upon opening of the main supply valve may be ignited by a gas pilot or by electrically energized spark producing means such as a spark plug. Prior types of electric ignition apparatus were usually arranged to be energized when the room thermostat called for heat and the main supply valve was thereby opened. After the gas was ignited, they were deene'rgized and remained thus until the thermostat again called for heat.

With such an arrangement, if the ignition system failed and the thermostat called for heat, gas would flow through the main control valve and accumulate in the furnace. The same result would occur if the flame after being ignited were extinguished by a downdraft or other cause. Also, if there should be any leakage of gas during periods of deenergization of the ignition means, it would accumulate in the furnace. Upon subsequent ignition of the furnace by actuation of the 2 ignition means when the thermostat called for heat or by any other means, the accumulated gas would be ignited, resulting in an explosion.

The present invention is designed to overcome all such hazards by preventing at all times the accumulation of an explosive mixture of gas in the furnace from any cause whatsoever. In one embodiment there is provided control apparatus for a furnace having a main gas supply valve controlling the supply of gas to the burner of the furnace. The control apparatus may comprise thermostatic means for controlling the normal operation of the valve, spark producing means for igniting fuel supplied to the burner, an ignition circuit for causing continuous cyclic energization of the spark-producing means, and means responsive to failure of said ignition means for effecting the closing of the valve and preventing the further supply of fuel therethrough.

An object of this invention is to provide control apparatus for a furnace which will continually energize the ignition device therefor at reguiar intervals so as to ignite any gas reaching the furnace between firings and prevent an explosive accumulation thereof.

A further object of the invention is to provide control apparatus of the type above referred to which automatically acts to prevent a supply of gas to the furnace upon any failure of the ignition means.

Still another object is to provide control apparatus for a furnace which acts to close the main fuel supply valve upon failure of the ignition means and render the thermostat normally controlling the operation of the valve ineffective thereafter to open said valve until correction of said failure.

A still further object is to provide control apparatus for a furnace that continually energizes the ignition means at regular intervals irrespective of whether or not the thermostat is calling for heat and has timing means for preventing opening of the main supply valve by operation of the thermostat until the ignition device has been energized.

Further objects and advantages will be apparent from the following description and claims when considered with the accompanying drawing. in which latter:

The single figure is a schematic representation of a furnace and a control system therefor embodying the present invention.

Referring more particularly to the drawing, the control apparatus embodying the invention is shown as applied to a gas fired furnace, although its use is not limited thereto. The gas is supplied through a conduit ill to a burner ii. A valve l2, shown diagrammatically, is provided in the conduit ill for controlling the flow of gas to the burner. The valve I: may be of a type well known in the art and having a valve seat |2 in which a plug or piston i4 is adapted to seat to close the valve. Extending outwardly from the valve body through an aperture in the casing I5 is a valve stem i5. The outer end of the valve stem preferably comprises the movable part or plunger of a solenoid |1 having a winding [1a A spring is positioned about the stem between the outer end of the casing l5 and a collar IS on the stem biases the valve plug H to closed position. When the winding |1a of the solenoid I1 is energized, the valve I2 is opened, and, as soon as the winding is deenergized. the valve is closed by the spring i2.

Gas supplied to the burner II is ignited by spark-producing means such as a spark plug 2|) which receives energy from the transformer 2|. This transformer comprises a primary winding 22 and a secondary winding 23 having a large number of turns relative to the primary winding so as to supply a high voltage impulse at the spark plug 25. An alternating current source 24 such as the ordinary 110 v. house circuit intermittently energizes the primary winding 22 of the transformer 2| due to the presence of an interrupter 25 in the circuit. The primary circuit of transformer 2| is as follows: From one side of source 24 through a switch 26, conductor 21, primary winding 22 of transformer 2|, conductors 28, 23 and 30, contacts 3| of the interrupter 25, and conductors 32 and 33, to the other side of source 24. The secondary or ignition circuit for energizing spark plug 25 consists of the inductive coupling between secondary winding 22 and primary winding 22 of transformer 2|, conductors 34 and 35, coil 36 of a relay 31, conductor 28, and spark plug 20, including the gap 29. The ignition circuit is a closed circuit with the ends shown as having ground connections coupled together.

The interrupter 25 which may be of the ordinary rotating cam type for opening and closing the contacts thereof is continuously driven by a motor 45. Current for the motor is provided from one side of source 24 through switch 25, conductors 21 and 4|, motor 45, conductors 42 and 42, normally closed relay contacts 45, conductors 45, 41 and 32 to the other side of the source 24.

With this construction, upon closing of the switch 25 the motor 45 drives interrupter 25 which periodically opens and closes contacts 2| causing periodic energization of the primary winding 22 of transformer 23. The motor operates continuously as long as the switch 26 is closed. Periodic energization of the primary winding 22 of the transformer 2| results in periodic energization of the secondary winding 22 and the spark plug 20 as above described. The interrupter is so arranged that the intervals between energization of the spark plug 20 will be sufficiently short to prevent an explosive accumulation of gas in the furnace and may be of the mostat circuit which in turn is energized by a transformer 52 comprising a primary winding 54 and a secondary winding 55. The thermostat circuit includes the inductive coupling between the primary winding 54 and the secondary winding 55 of the transformer 52, conductor 55, room thermostat 51 having the usual contacts, conductor 52, normally closed relay contacts 52, conductor 55, the winding 55a of relay 52, and conductor 5| Assuming that the valve I2 is closed and the room thermostat calls for heat, the thermostat circuit is initially energized through the transformer 53 by the following circuit: From one side of source 24 through the switch 25, conductors 21 and 52, primary winding 54 of transformer 52, conductor 52, normally closed relay contacts 54 and 54a, conductors 55, 65 and 51. a second pair of contacts 55 of interrupter 25, and conductors 53 and 23 to the other side of source 24. Energization of this circuit when the contacts 55 of the interrupter 25 are closed causes current to flow through the thermostat circuit including the relay 52. Energization of the relay 52 closes relay contacts 43 and contacts 54a and 15, and opens contacts 64 and 64a. The contact 15 is actuated, however, to closed position before contact 54 is moved to open position.

Upon the closing of the relay contacts 54a and 15, current is continuously supplied to the thermostat circuit by the following circuit: From one side of source 24 through switch 26, conductors 21 and 52, primary winding 54 of transformer 53, conductor 53, contacts 54a and 15, and conductors 1| and 33 to the other side of the source 24. This circuit when energized continuously energizes the thermostat circuit including the relay 52 and maintains the relay contacts 43 in the valve circuit closed. The main supply valve I2 is then open. Such condition normally continues until the thermostat no longer calls for heat and breaks the thermostat circuit permitting the relay 52 to become deenergized and thereby open contacts 49 and 10 while closing contact 54.

The interrupter 25 is so arranged that the contacts 3| are first closed and shortly thereafter contacts 63 are closed. Both sets of contacts 2| and 55 are opened simultaneously.

The arrangement heretofore discussed is that which controls the normal operation of the control apparatus. Once the switch 25 has been closed the normal operation of the apparatus is as follows: The motor 40 runs continuously to operate the interrupter 25. If the thermostat is not calling for heat, periodic closing of the contacts 2| merely causes intermittent energization of the spark plug 20 through the intermediary of the transformer 2|. The intermittent energization of the spark plug 20 continually ignites any gas which might be supplied to the burner I I before there is a sufficient accumulation thereof to cause an explosion. However, when the room thermostat 51 calls for heat, primary winding 54 of the transformer 52 being energized by the closing action of contacts 53 at interrupter 25, the coil of relay 52 will be energized long enough to close the relay contacts 49 of the valve circuit and also contacts 15 and 54a, and then to open contacts 64 and 54a. The closing of contact 10 with contact 54 places primary 54 of transformer 53 in circuit with the current supply 24 by wires 52 and 1| to maintain thereby a continuous current supply and thus by-pass the interru-pter contacts 65. Contacts 45 are thus held closed to keep valve I3 open as long as room thermostat 51' calls for heat.

In order to provide for possible failure of the ignition circuit, a control circuit responsive to failure of the ignition circuit is provided. This control circuit is opened and closed by the relay 31 comprising a coil 36 in the ignition circuit having an iron core I2.- The core 12 when energized attracts the armature I4 to open contacts I5 in the control circuit. The control circuit is energ'ized by energization of the transformer 18 and includes secondary winding 11 of the transformer I6, conductor 18, contacts 15, conductor I8, coil 8|! of a relay 8| and conductor 8!. Relay 8| includes the coil 88 and an iron core 83. It controls contacts 58 in the thermostat circuit and contacts 45 in the motor circuit, both of which are normally closed and are opened upon energization of the relay coil 86. It also controls contacts 84. Contacts 84 are in a warning light circuit and are normally open, being closed by energization of the relay coil 88. The primary circuit of transformer 16 is as follows: Source 24, switch 26, conductors 21 and 85, primary winding 86 of the transformer 16, conductors 81 and 61, contacts 68 of the interrupter and conductors 88 and 33 to the other side of the source.

As previously stated, contacts 3| are closed slightly in advance of contacts 68. Consequently, relay 31 will function to open cont cts 15 in the circuit of relay 8| before contacts 68 are closed to energize this circuit. The circuit of relay 8| cannot therefore be energized before relay 31 acts to open contacts I5. However, upon failure of the ignition circuit, the relay 31 will remain deenergized, or, if energized. will immediately become and thereafter remain deenergized, thereby permitting contacts 15 to close and thereby close the control circuit. When this occurs, energization of the transformer I6 will energize the coil 88 of relay 8| and open relay contacts 58 in the room thermostat circuit and contacts 45 in the motor circuit. It will also be observed that with contacts 3| and 68 acting to open simultaneously. there will be no delay in the action of the circuit of relay 3'! or in this relay itself which will cause contacts 15 to close at a time when the circuit of relay 8| is ready to establish a flow of current at a time contacts 68 are in closed position. Opening of the contacts 58 in the thermostat circuit will effect opening of the contacts 48 in the valve circuit to deenergize the valve circuit and permit the valve l2 to close. Also, opening of the contacts 45 will cut off current to the motor, stooping the motor and the interrupter. In order to maintain the contacts 59 and 45 open, the control circuit must be energized to keep the relay coil 80 energized. This is accomplished by the interrupter due to the cam arrangement causing the motor always to stop at a position holding contacts 3| and 68 closed. If desired, other known means may be employed to maintain the contacts 45 and 58 open.

It is thus to be seen that with the present invention. when the system is operating normally, I

the spark plug is periodically energized at short intervals to ignite any gas supplied to the burner before an explosive amount accumulates, and the room thermostat serves to control the operation of the main gas supply v lve l2. there should be a failure of the ignit on circuit, the control circuit acts to effect the closing of the main gas supply valve I2 and discontinue operation of the motor.

If desired a warning light circuit may also be- However, if

6 incorporated which will light a lamp upon en-v ergization of the control circuit. The warning light circuit is as follows: From source 24 through switch 26, conductors 21 and 88, lamp: 88, conductor 96, relay contacts 84 and conductors SI, 41 and 83 to the other side of the source. As relay contact 84 is closed upon actuation of the relay 8| the warning light 88 will be lighted upon v failure of the ignition system.

To assure a full and extended spark that will ignite the gas mixture at all times when necessary, a condenser 73 may be connected as shown, or in any suitable way,

It is considered advantageous in the normal functioning of the arrangement herein disclosed, after it is placed in operation, that the circuit of the room thermostat 51 is removed from the direct control of motor 48 so that it will function to keep the valve 3 he d open, when the room thermostat calls for heat, without being interrupted by the repeated opening and closing of the interrupter switch 68. As previously explained, this is accomplished by the opening of contact 64 in the circuit including wires 65 and 66 that receive current through wire 61 connected beyond interrupter switch 68. When contact 64 is opened, contact 18 is engaging contact 64a to connect primary coil 54 of transformer 53 directly across wires 21 and 33 leading from the source of current 24. With this relation established, current will flow through the coil 66a of relay 52 to hold the same energized and the contacts 64 closed as long as the room thermostat 51 remains closed. With contacts 64 in closed position, the fuel valve I! will remain open. .The

safety control prevents valve l2 remaining open if the ignition circuit should fail at any time. Instantly, upon failure of the ignition circuit, contacts 15 will close and current will flow through the circuit of relay 8| when contacts 68- of the interrupter close whereby energization of relay 8| will open contacts 58 to break the circuit of relay 52. This immediately causes contacts 48 to open and to close'valve '2, the latter remaining closed until the ignition circuit will again function properly.

Without further elaboration, the foregoing will so fully explain the gist of my invention that others may, by applying current knowledge, readily adapt the same for use under varying conditions of service, without eliminating certain features, which may properly be said to constitute the essential items of novelty involved, which items are intended to be defined and secured to me by the following claims.

I claim:

1. Control apparatus for a furnace having a fuel supply line, valve means in said fuel supply line and temperature responsive means for normally controlling the supply of fuel to the burner of said furnace, comprising spark producing means adapted to be positioned to ignite directly fuel supplied to said burner, energization means independent of said temperature responsive means for continually energizing said spark producing means, and means responsive to failure of said energization means for preventing the flow of fuel to said furnace.

2. Control apparatus for a furnace having a fuel supply line, valve means in said fuel supply line and temperature responsive means for normally controlling the supply of fuel to the burner of said furnace, comprising spark producing means adapted to be positioned to ignite directly fuel supplied to said burner, energization means including an interrupter independent of said temperature responsive means for continually energizing said spark producing means, a motor for continuously operating said interrupter, and means responsive to failure of said energization means for preventing the flow of fuel to said burner.

3. Control apparatus for a furnace having a valve for controlling the supply of fuel to the burner of said furnace, comprising a circuit having therein means responsive to a condition for controlling the operation of said valve, spark producing means adapted to be positioned to ignite directly fuel supplied to said burner. energization means independent of said means responsive to a condition for continually energizing said spark producing means, and means responsive to failure of said energization means for controlling the operation of said valve to prevent the supply of fuel to said burner.

4. Control apparatus for a furnace having a valve for controlling the supply of fuel to the burner of said furnace, comprising a circuit including temperature responsive means for controlling the operation of said valve, an ignition circuit including spark producing means adapted to be positioned to ignite directly fuel supplied to said burner, energization means independent of said temperature responsive means for continually energizing said ignition circuit, and means responsive to failure of said ignition circuit to affect said temperature responsive means circuit to prevent the flow of fuel to said burner.

5. Control apparatus for a furnace having a valve for controlling the supply of fuel to the burner of said furnace, comprising a circuit including temperature responsive means for controlling the operation of said valve, an ignition circuit including spark producing means adapted to be positioned to ignite directly fuel supplied to said burner, energization means independent of said temperature responsive means for continually energizing said ignition circuit, and a control circuit responsive to failure of said ignition circuit to render said temperature responsive means circuit ineffective to permit the flow of fuel to said burner.

6. Control apparatus for a furnace having a normally closed valve for controlling the supply of fuel to the burner of said furnace, comprising a circuit including thermostatic means for controlling the operation of said valve, an ignition circuit including spark producing means adapted to be positioned to ignite directly fuel supplied to said burner, a control circuit having means foropening said thermostatic means circuit and rendering it ineffective to control the operation of said valve when said control circuit is energized, a source of energy for said circuits, energization means independent of said thermostatic means for continually energizing said ignition circuit, and means normally preventing energization of said control circuit and responsive to failure of said ignition circuit for effecting energization of said control circuit.

7. Control apparatus for a furnace having a normally closed valve for controlling the supply of fuel to the burner of said furnace, comprising a circuit including thermostatic means for controlling the operation of said valve, an ignition circuit including spark producing means adapted to be positioned to ignite directly fuel supplied to said burner, a control circuit, relay means responsive to energization of said control circuit for opening said thermostatic means circuit and rendering it ineffective to control the operation of said valve, a source of energy for said circuits,

energization means independent of said thermostatic means for continually energizing said ignition circuit, and means normally preventing energization of said control circuit and responsive to failure of said ignition circuit for effecting energization of said control circuit.

8. Control apparatus for a furnace having a normally closed valve for controlling the supply of fuel to the burner of said furnace, comprising a circuit including thermostatic means for controlling the operation of said valve, an ignition circuit including spark producing means adapted to be positioned to ignite directly fuel supplied to said burner, a control circuit, relay means responsive to energization of said control circuit for opening said thermostatic means circuit and rendering it ineffective to control the operation of said valve, a source of energy for said circuits, energization means independent of said thermostatic means for continually energizing said ignition circuit, and relay means responsive to energization of said ignition circuit for preventing energization of said control circuit and responsive to failure of said ignition circuit to effect energization of said control circuit.

9. Control apparatus for a furnace having a normally closed valve for controlling the supply of fuel to the burner of said furnace, comprising a circuit including thermostatic means for controlling the operation of said valve, an ignition circuit including spark producing means adapted to be positioned to ignite directly fuel supplied to said burner, means for causing continual intermittent energization of said ignition circuit, a control circuit having means for opening said thermostatic circuit and rendering it ineffective to control the operation of said valve when said control circuit is energized, a source of energy for said circuits, and means normally preventing energization of said control circuit and responsive to failure of said ignition circuit for effecting energization of said control circuit.

10. Control apparatus for a furnace having a normally closed valve for controlling the supply of fuel to the burner of said furnace, comprising a circuit including thermostatic means, a valve circuit for opening said valve, means responsive to energization of said thermostatic means circuit for effecting energization of said valve circuit, an ignition circuit including spark producing means adapted to be positioned to ignite directly fuel supplied to said burner, a source of energy for said circuits, energization means independent of said thermostatic means for continually energizing said ignition circuit, and means responsive to failure of said ignition circuit for opening said thermostat circuit and Q preventing the flow of fuel to said burner.

11. Control apparatus for a furnace having a normally closed valve for controlling the supply of fuel to the burner of said furnace, comprising a circuit including a thermostat, a valve circuit 08 for opening said valve, means responsive to energization of said thermostat circuit for effecting energization of said valve circuit to open said valve, a circuit having means for intermittently energizing it inductively coupled to energize said I. thermostat circuit, a holding circuit for continuously energizing said thermostat circuit when inductively coupled thereto, means responsive to energization of said thermostat circuit by said intermittently energized circuit to couple said I thermostat circuit to said holding circuit, an

ignition circuit including spark producing means adapted to [be positioned to ignite directly fuel supplied to said burner, a source of energy for said circuits, energization means independent of said thermostat circuit for energizing said ignition circuit, and means responsive to failure of said ignition circuit for opening said thermostat circuit and preventing the flow of fuel to said burner.

12. Control apparatus for a furnace having a normally closed valve for controlling the supply of fuel to the burner of said furnace, comprising a circuit including a thermostat, a valve circuit for opening said valve, means responsive to energization of said thermostat circuit for effecting energization of said valve circuit to open said valve, a circuit having means for intermittently energizing it inductively coupled to energize said thermostat circuit, a holding circuit for continuously energizing said thermostat circuit when inductively coupled thereto, means responsive to energization of said thermostat circuit by said intermittently energized circuit to couple said thermostat circuit to said holding circuit, an

ignition circuit including spark producing means adapted to be positioned to ignite directly fuel supplied to said burner, a source of energy for said circuits, means independent of said thermostat circuit for causing continual intermittent energization of said ignition circuit, and means responsive to failure of said ignition circuit for opening said thermostat circuit and preventing the flow of fuel to said burner.

13. Control apparatus for a furnace having a normally closed valve for controlling the supply of fuel to the burner of said furnace, comprising a circuit including a thermostat, a valve circuit for opening said valve, means responsive to energization of said thermostat circuit for effecting energization of said valve circuit to open said valve, a circuit having an interrupter therein for eflecting intermittent energization thereof inductively coupled to energize said thermostat circuit, a holding circuit for continuously energizing said thermostat circuit when inductively coupled thereto, means responsive to energization of said thermostat circuit by said intermittently energized circuit to couple said thermostat circuit to said holding circuit, spark producing means adapted to be positioned to ignite directly fuel supplied to said burner, a circuit including an interrupter for energizing said spark producing means, a source of energy for said circuits, said interrupters being so arranged that the inierrupter ii said ignition circuit is closed first and remains closed until said other interrupter closes, a motor for continuously operating said interrupters, and means responsive to failure of said ignition circuit for stopping said motor. 14. Automatically operating control appara for a furnace having a valve biased to clos position for controlling the supply of fuel to the burner of said furnace, comprising a circuit including means responsive to a condition for operating said valve to open position when said circuit is energized, spark producing means adapted to be positioned to ignite directly fuel supplied to said burner, means for causing continual intermittent energization of said spark producing means irrespective of whether or not said circuit is energized, and means responsive to failure of said spark producing means for controlling said valve to prevent the flow of fuel to said burner.

15. Automatically operating control apparatus 10 for a furnace having a valve biased to closed position for controlling the supply of fuel to the burner of said furnace comprising a circuit including thermostatic means for operating said valve to open position when said circuit is energized, spark producing means adapted to be positioned to ignite directly fuel supplied to said burner, an ignition circuit including an interrupter for causing continual intermittent energization of said spark producing means irrespective of whether or not said thermostatic circuit is energized, and means responsive to failure of said spark producing circuit for controlling said valve to prevent the flow of fuel to said burner.

16. Control apparatus for a furnace having a fuel supply line, valve means in said fuel supply line and means responsive to a condition for normally controlling the supply of fuel to the burner of said furnace, comprising spark producing means adapted to [be positioned to ignite directly fuel supplied to said burner, energization means independent of said responsive means for continually supplying energy impulses to said sparkproducing means, and means responsive to failure of said energization means for controlling said valve means to prevent the flow of fuel to said furnace.

17. Control apparatus for a furnace having a burner, a fuel supply line for said burner and valve means in said supply line for controlling the supply of fuel to said burner, comprising spark producing means adapted to be positioned to ignite directly fuel supplied to said burner, energization means independent of said responsive means for continually supplying energy impulses to said spark producing means of sumciently high voltage to ignite fuel supplied to the burner, and means responsive to failure of said energization means for controlling said valve means to prevent the flow of fuel to said furnace.

18. Control apparatus for a furnace havinga burner, a fuel supply line for said burner and valve means in said supply line for controlling the supply of fuel to said burner, comprising spark producing means adapted to be positioned to ignite directly fuel supplied to said burner, energization means including a high voltage circuit independent of the operation of said responsive means for continually supplying energy impulses to said spark producing means of sufliciently high voltage to ignite fuel supplied to said burner, and means responsive to lack of energization of said high voltage circuit for controlling said valve means to prevent the flow of fuel to said furnace.

- JOHN S. BAKER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

